The present invention concerns a process for the production of 3,3-dichloro-2-methylpropene by reacting 1-chloro-2-methylpropene with sulfuryl chloride.
3,3-dichloro-2-methylpropene is important as an intermediate for organic syntheses on account of its functional groups, namely geminal chlorine substituents as well as a double bond. For example, this product can be used as an intermediate for the preparation of certain Benzofuranes in analogy to EP 0 040 400 which are useful as soil insecticides. Besides that this product can be used itself as a component for insecticides as described in Chem. Abstr. 76 (1972) 122592j.
This product heretofore has not been readily available since it is not obtained, either as a main product or as a by-product, in the industrial gaseous-phase chlorination of isobutene.
Production of 3,3-dichloro-2-methylpropene is possible, with low yield of about 6%, by the introduction of gaseous chlorine, in stoichiometric excess, into boiling 1-chloro-2-methylpropene, under the exclusion of light [A. L. Henne et al., J. Am. Chem. Soc. 72 : 3577 (1950)]. This process is unsuited for an industrially satisfactory manufacture on account of low selectivity.
It is also known that 3,3-dichloro-2-methylpropene can be produced by reacting 1-chloro-2-methylpropene with chlorine in the presence of NaHCO.sub.3 in a molar ratio of 1:1:1.5 at 0.degree. C., yielding, besides 68%, 3,3-dichloro-2-methylpropene, 32% 1,1,2-trichloro-2-methylpropane [Chem. Abstr. 33 : 4190 (1939)]. This process is likewise unsatisfactory since it necessitates the use and separation of solid and, moreover, expensive cooling must be provided. The yield is likewise inadequate in this process.